The Johns Hopkins Pediatric Liver Center Staff cares for ~1000 patients and, in the last two years for 111 children who have one of the liver diseases studied by the BARC/CLiC/CFLD multi-center study groups in which we have been participating. The purpose of this ChiLDREN proposal is to devote the resources of the Johns Hopkins Pediatric Liver Center to achieve the following 6 Specific Aims: 1) Continue our participation in BARC and CLiC by providing clinical data and biospecimens for discovery of new diagnostics, etiologic and treatment options for children with the BARC and CLiC liver diseases. Continue our site's involvement in the BARC START trial by enrolling new participants. 2) Expand our ongoing study of the Role of Rotavirus in "Human Biliary Atresia";this is a study in which we are investigating sera from BA and genetic cholestatic control infants (provided to us in an Ancillary Study approved by the BARC Steering Committee) for evidence of humoral immunity to rotavirus and to rotavirus-infected cholangiocytes. 3) Continue our participation in the prospective longitudinal study of cystic fibrosis liver disease (CFLD) aimed at identifying predictors of development of liver disease and of outcome. 4) Continue to provide training opportunities for investigators in pediatric liver disease, as exemplified by our proposal to train one of our first year fellows in pediatric gastroenterology in clinical care and research related to CFLD. Her project is to identify the best noninvasive markers of liver fibrosis in children with CFLD. 5) Continue to provide education about pediatric liver diseases to the scientific and lay communities through publications and the BARC and CLiC websites, with a particular focus on soliciting feedback regarding the websites from the families who use it. 6) Continue the established infrastructure we have already created to perform BARC, CLiC, and CFLD. We are committed to participation in this multi-center study group and believe that through this group it will be possible to make major progress in the goal of improving the health of children with these serious pediatric liver diseases. Relevance: The relevance of our proposal is that we believe that the best way to accomplish the goal of improving the health of children with the liver diseases we are studying is via this multi-center approach in which we have already been actively participatin. Our studies of the Role of Rotavirus in Human Biliary Atresia have the potential of providing better, more rapid diagnostic and can ultimately lead to more rational immunotherapy and prevention of this very serious infantile liver disease.